Symmetric plasma process chamber

ABSTRACT

Embodiments of the present invention provide a plasma chamber design that allows extremely symmetrical electrical, thermal, and gas flow conductance through the chamber. By providing such symmetry, plasma formed within the chamber naturally has improved uniformity across the surface of a substrate disposed in a processing region of the chamber. Further, other chamber additions, such as providing the ability to manipulate the gap between upper and lower electrodes as well as between a gas inlet and a substrate being processed, allows better control of plasma processing and uniformity as compared to conventional systems.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of co-pending U.S. patentapplication Ser. No. 13/629,267, filed on Sep. 27, 2012, which claimsbenefit of U.S. Provisional Patent Application Ser. No. 61/543,565,filed on Oct. 5, 2011. Each afore mentioned patent application isincorporated herein by reference.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention generally relates to a plasma processing apparatusfor fabricating substrates in which plasma is excited by RF powerapplied between electrodes. More specifically, the present inventionrelates to a plasma processing chamber that provides electrical, gasflow, and thermal symmetry for improved plasma uniformity control.

Description of the Related Art

Electronic devices, such as flat panel displays and integrated circuitscommonly are fabricated by a series of process steps in which layers aredeposited on a substrate and the deposited material is etched intodesired patterns. The process steps commonly include physical vapordeposition (PVD), chemical vapor deposition (CVD), plasma enhanced CVD(PECVD), and other plasma processing. Specifically, a plasma processrequires supplying a process gas mixture to a vacuum chamber, andapplying electrical or electromagnetic power (RF power) to excite theprocess gas into a plasma state. The plasma decomposes the gas mixtureinto ion species that perform the desired deposition or etch processes.

One problem encountered with plasma processes is the difficultyassociated with establishing uniform plasma density over the substratesurface during processing, which leads to non-uniform processing betweenthe center and edge regions of the substrate. One reason for thedifficulty in establishing uniform plasma density involves naturalelectrical, gas flow, and thermal skews due to asymmetry in the physicalprocess chamber design. Such skews not only result in naturally,azimuthal, non-uniform plasma density, but also make it difficult to useother processing variables or “knobs” to control center-to-edge plasmauniformity.

Therefore, a need exists for a plasma processing apparatus that improveselectrical, gas flow, and thermal symmetry for improved plasmauniformity control.

SUMMARY OF THE INVENTION

In one embodiment of the present invention, a plasma processingapparatus is provided that comprises a lid assembly and a chamber bodyenclosing a processing region. A substrate support assembly is disposedin the chamber body. An exhaust assembly defining an evacuation regionwithin the chamber body is provided. The chamber body includes aplurality of passages symmetrically disposed about a central axis of thesubstrate support assembly fluidly connecting the processing region withthe evacuation region. The substrate support assembly comprises a lowerelectrode and a support pedestal disposed in a central region fluidlysealed from the processing and evacuation regions. A plurality of accesstubes are positioned through the chamber body to provide access to thecentral region and arranged symmetrically about the central axis of thesubstrate support assembly.

In another embodiment, a plasma processing apparatus comprises a lidassembly and a chamber body enclosing a processing region. A substratesupport assembly is disposed in the chamber body. The lid assemblycomprises an upper electrode having a central manifold configured todistribute processing gas into the processing region and one or moreouter manifolds configured to distribute processing gas into theprocessing region. The lid assembly also comprises a ring manifoldcoupled to the one or more outer manifolds via a plurality of gas tubesarranged symmetrically about a central axis of the substrate supportassembly.

In yet another embodiment, a plasma processing apparatus comprises a lidassembly and a chamber body enclosing a processing region. A substratesupport assembly is disposed in the chamber body. An upper liner isdisposed within the chamber body circumscribing the processing region.The upper liner has a cylindrical wall with a plurality of slotsdisposed therethrough and arranged symmetrically about a central axis ofthe substrate support assembly. A backing liner is coupled to thecylindrical wall covering at least one of the plurality of slots. A meshliner annularly disposed about the substrate support assembly andelectrically coupled to the upper liner.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a schematic, cross-sectional view of a plasma processingapparatus according to one embodiment of the present invention.

FIG. 2 is a schematic, top view of an upper electrode of the processingapparatus of FIG. 1.

FIG. 3A is a schematic, isometric view of an upper liner assembly thatis disposed within an upper portion of a chamber body circumscribing aprocessing region of the processing apparatus of FIG. 1.

FIG. 3B is a partial, cross-sectional view of a portion of the chamberbody and the upper liner assembly.

FIG. 4 is a schematic view of the processing apparatus taken along line4-4 shown in FIG. 1.

FIG. 5 is a schematic depiction of the layout of access tubes extendingthrough the processing apparatus of FIG. 1.

DETAILED DESCRIPTION

As previously mentioned, a problem in conventional plasma systems is thedifficulty in providing uniform plasma density due to asymmetry in thechamber. Embodiments of the present invention mitigate this problem byproviding a chamber design that allows extremely symmetrical electrical,thermal, and gas flow conductance through the chamber. By providing suchsymmetry, plasma formed within the chamber naturally has improveduniformity across the surface of a substrate disposed in a processingregion of the chamber. Further, other chamber additions, such asproviding the ability to manipulate the gap between upper and lowerelectrodes as well as between a gas inlet and a substrate beingprocessed, provides a large process window that enables better controlof plasma processing and uniformity as compared to conventional systems.

FIG. 1 is a schematic, cross-sectional view of a plasma processingapparatus 100 according to one embodiment of the present invention. Theplasma processing apparatus 100 may be a plasma etch chamber, a plasmaenhanced chemical vapor deposition chamber, a physical vapor depositionchamber, a plasma treatment chamber, an ion implantation chamber, orother suitable vacuum processing chamber. As shown in FIG. 1, the plasmaprocessing apparatus 100 generally includes a chamber lid assembly 110,a chamber body assembly 140, and an exhaust assembly 190, whichcollectively enclose a processing region 102 and an evacuation region104. In practice, processing gases are introduced into the processingregion 102 and ignited into a plasma using RF power. A substrate 105 ispositioned on a substrate support assembly 160 and exposed to the plasmagenerated in the processing region 102 to perform a plasma process onthe substrate 105, such as etching, chemical vapor deposition, physicalvapor deposition, implantation, plasma annealing, plasma treating,abatement, or other plasma processes. Vacuum is maintained in theprocessing region 102 by the exhaust assembly 190, which removes spentprocessing gases and byproducts from the plasma process through theevacuation region 104.

The lid assembly 110 generally includes an upper electrode 112 (oranode) isolated from and supported by the chamber body assembly 140 anda chamber lid 114 enclosing the upper electrode 112. FIG. 2 is aschematic, top view of the upper electrode 112. The upper electrode 112is coupled to an

RF power source 103 via a conductive gas inlet tube 126. The conductivegas inlet tube 126 is coaxial with a central axis (CA) of the chamberbody assembly 140 so that both RF power and processing gases aresymmetrically provided. The upper electrode 112 includes a showerheadplate 116 attached to a heat transfer plate 118. The showerhead plate116, the heat transfer plate 118, and the gas inlet tube 126 are allfabricated from a RF conductive material, such as aluminum or stainlesssteel.

The showerhead plate 116 has a central manifold 120 and one or moreouter manifolds 122. The one or more outer manifolds 122 circumscribethe central manifold 120. The central manifold 120 receives processinggases from a gas source 106 through the gas inlet tube 126 anddistributes the received processing gases into a central portion of theprocessing region 102 through a plurality of gas passages 121. The outermanifold(s) 122 receives processing gases, which may be the same or adifferent mixture of gases received in the central manifold 120, fromthe gas source 106. The outer manifold(s) 122 then distributes thereceived processing gases into an outer portion of the processing region102 through a plurality of gas passages 123. The manifolds 120, 122 havesufficient volume to function as a plenum so that uniform pressure isprovided to each gas passage 121 associated with a respective manifold120, 122. The dual manifold configuration of the showerhead plate 116allows improved control of the delivery of gases into the processingregion 102. For instance, processing gases provided to the centralportion of the processing region 102, and thus the central portion ofthe substrate 105 positioned therein, may be introduced at a differentflow rate and/or pressure than the processing gases provided to theouter portion of the processing region 102, and thus outer portion ofthe substrate 105. The multi-manifold showerhead plate 116 enablesenhanced center to edge control of processing results as opposed toconventional single manifold versions.

Referring to FIGS. 1 and 2, it can be seen that a processing gas fromthe gas source 106 is delivered through an inlet tube 127 into a ringmanifold 128 concentrically disposed around the inlet tube 126. From thering manifold 128, the processing gas is delivered through a pluralityof gas tubes 129 to the outer manifold(s) 122. In one embodiment, thering manifold 128 includes a recursive gas path to assure that gas flowsequally from the ring manifold 128 into the gas tubes 129. The ringmanifold 128 and the gas tubes 129 are fabricated from a conductivematerial, such as aluminum or stainless steel. Thus, the ring manifold128 and the gas tubes 129 may influence the symmetry of the RF current,causing skewing of the electric field provided by the upper electrode112, potentially resulting in an effect in the plasma uniformity withinthe process region 102.

To prevent such skewing in the electric field, the gas tubes 129 arepositioned symmetrically about the central axis (CA) extendingvertically through the processing apparatus 100. Thus, the gas tubes 129extend from the centrally located ring manifold 128 at equidistantangles (A) to deliver the processing gas through the cooling plate 118and into the outer manifold(s) 122. For example, the embodiment shown inFIG. 2 depicts three gas tubes 129 spaced apart by 120 degree angles. Inother examples (not shown), more or fewer gas tubes 129 may be used aslong as they are positioned symmetrically about the central axis (CA),i.e., at equidistant angles (A) from one another. By employing aring-shaped manifold and arranging the gas tubes 129 symmetrically aboutthe central axis (CA), the electrical symmetry of the upper electrode112 is significantly improved over conventional systems resulting inmore uniform and consistent plasma formation in the processing region102. Additionally, the symmetric arrangement of the gas tubes 129provides gas in a uniformly polar array into the outer manifold 122,thereby providing azimuthal uniform pressure distribution within theouter manifold 122 and consequently, an azimuthally uniform flow of gasthrough the gas passages 123 into the processing region 102, therebyenhancing processing uniformity.

A heat transfer fluid is delivered from a fluid source 109 to the heattransfer plate 118 through a fluid inlet tube 130. The fluid iscirculated through one or more fluid channels 119 disposed in the heattransfer plate 118 and returned to the fluid source 109 via a fluidoutlet tube 131. Suitable heat transfer fluids include water,water-based ethylene glycol mixtures, a perfluoropolyether (e.g.,Galden® fluid), oil-based thermal transfer fluids, or similar fluids.

The fluid inlet tube 130 and fluid outlet tube 131 are each fabricatedfrom a non-conductive material, such as a suitable plastic material.Thus, the tubes themselves do not affect the electrical symmetry of theupper electrode 112. However, the fittings 132 are fabricated from aconductive material, such as aluminum or stainless steel, and thus mayaffect the electrical symmetry of the upper electrode 112 causing askewing effect. Thus, conductive plugs 133, fabricated from the samematerial and having the same size and shape as the fittings 132, aredisposed symmetrically about the central axis (CA) as shown in FIG. 2such that the plugs 133 and fittings 132 together define a polar arraycentered about the central axis (CA) of the chamber body assembly 140.The addition of the conductive plugs 133 improve the electrical symmetryof the upper electrode 112, resulting in more uniform and consistentplasma formation in the processing region 102 than available inconventional systems.

Referring back to FIG. 1, the chamber body assembly 140 includes achamber body 142 fabricated from a conductive material resistant toprocessing environments, such as aluminum or stainless steel. Thesubstrate support assembly 160 is centrally disposed within the chamberbody 142 and positioned to support the substrate 105 in the processingregion 102 symmetrically about the central axis (CA).

FIG. 3A is a schematic, isometric view of an upper liner assembly 144that is disposed within an upper portion of the chamber body 142circumscribing the processing region 102. The upper liner assembly 144may be constructed from a conductive, process compatible material, suchas aluminum, stainless steel, and/or yttria (e.g., yttria coatedaluminum). In practice, the upper liner assembly 144 shields the upperportion of the chamber body 142 from the plasma in the processing region102 and is removable to allow periodic cleaning and maintenance. In oneembodiment, the upper liner assembly 144 is temperature controlled, suchas by an AC heater (not shown) in order to enhance the thermal symmetrywithin the chamber and symmetry of the plasma provided in the processingregion 102.

Referring to FIGS. 1 and 3A, the chamber body 142 includes a ledge 143that supports an outer flange 145 of the upper liner assembly 144. Aninner flange 146 of the upper liner assembly 144 supports the upperelectrode 112. An insulator 113 is positioned between the upper linerassembly 144 and the upper electrode 112 to provide electricalinsulation between the chamber body assembly 140 and the upper electrode112.

The upper liner assembly 144 includes an outer wall 147 attached to theinner and outer flanges (146,145), a bottom wall 148, and an inner wall149. The outer wall 147 and inner wall 149 are substantially vertical,cylindrical walls. The outer wall 147 is positioned to shield chamberbody 142 from plasma in the processing region 102, and the inner wall149 is positioned to at least partially shield the side of the substratesupport assembly 160 from plasma in the processing region 102. Thebottom wall 148 joins the inner and outer walls (149, 147) except incertain regions where evacuation passages 189 are formed, which aresubsequently discussed herein.

Referring back to FIG. 1, the processing region 102 is accessed througha slit valve tunnel 141 disposed in the chamber body 142 that allowsentry and removal of the substrate 105 into/from the substrate supportassembly 160. The upper liner assembly 144 has a slot 150 disposedtherethrough that matches the slit valve tunnel 141 to allow passage ofthe substrate 105 therethrough. The chamber body assembly 140 includes aslit valve door assembly 151 that includes an actuator 152 positionedand configured to vertically extend a slit valve door 153 to seal theslit valve tunnel 141 and slot 150 and to vertically retract the slitvalve door 153 to allow access through the slit valve tunnel 141 andslot 150. The slit valve door assembly 151 and its components are nothatched in FIG. 1 in order to minimize drawing clutter. The slit valvedoor 153 may be constructed of a material substantially matching that ofthe upper liner assembly 144 (e.g., yttria coated aluminum) in order toprovide increased electrical symmetry in the liner. In one embodiment,the slit valve door 153 is temperature controlled, such as by an ACheater (not shown), to match the temperature of the upper liner assembly144 to provide increased thermal symmetry in the processing region 102.

Referring to FIG. 3A, additional slots 154, substantially matching thesize and shape of slot 150, are disposed through the upper linerassembly 144. The slots 154 are disposed through the upper linerassembly 144 symmetrically about the central axis (CA). For example, asshown in FIG. 3A, two slots 154 are disposed at angles of 120 degreesfrom the slot 150, such that the slot 150 and slots 154 form a polararray about the central axis (CA). The slots 154 are disposedsymmetrically about the upper liner assembly 144 in order to compensatefor changes in the electrical current density and/or distributionpresent in the upper liner assembly 144 due to the presence of the slot150. In addition, the slots 150 and 154 may be positioned in line withrespective gas tubes 129 to provide improved electrical symmetry in thechamber.

FIG. 3B is a partial, cross-sectional view of a portion of the chamberbody 142 and the upper liner assembly 144. Backing liners 155 may beprovided, attached to and covering, the slots 154 of the upper linerassembly 144. The backing liners 155 are sized, shaped, and constructedof materials to mimic the slit valve door 153. The backing liners 155are also in conductive contact with the upper liner assembly 144 tomaintain electrical and thermal contact with the upper liner assembly144. Thus, the backing liners 155 further provide electrical as well asthermal symmetry about the upper liner assembly 144 in order to enablemore uniform plasma density within the processing region 102 than isavailable with conventional systems.

FIG. 4 is a schematic view of the processing apparatus 100 taken alongline 4-4 shown in FIG. 1 with the substrate 105 removed for clarity.Referring to FIGS. 1 and 4, the substrate support assembly 160 isdisposed centrally within a central region 156 of the chamber bodyassembly 140 and sharing the central axis (CA). That is, the centralaxis (CA) passes vertically through the center of the substrate supportassembly 160. The substrate support assembly 160 generally includeslower electrode 161 (or cathode) and a hollow pedestal 162, the centerof which the central axis (CA) passes through, and is supported by acentral support member 157 disposed in the central region 156 andsupported by the chamber body 142. The central axis (CA) also passesthrough the center of the central support member 157. The lowerelectrode 161 is coupled to the RF power source 103 through a matchingnetwork (not shown) and a cable (not shown) routed through the hollowpedestal 162 as will be subsequently described. When RF power issupplied to the upper electrode 112 and the lower electrode 161, anelectrical field formed therebetween ignites the processing gasespresent in the processing region 102 into a plasma.

The central support member 157 is sealed to the chamber body 142, suchas by fasteners and o-rings (not shown), and the lower electrode 161 issealed to the central support member 157, such as by a bellows 158.Thus, the central region 156 is sealed from the processing region 102and may be maintained at atmospheric pressure, while the processingregion 102 is maintained at vacuum conditions.

An actuation assembly 163 is positioned within the central region 156and attached to the chamber body 142 and/or the central support member157. Note, the actuation assembly 163 is shown without hatching tominimize drawing clutter. The actuation assembly 163 includes anactuator 164 (e.g., motor), a lead screw 165, and a nut 166 attached tothe pedestal 162. In practice, the actuator 164 rotates the lead screw165, which, in turn raises or lowers the nut 166, and thus the pedestal162. Since the lower electrode 161 is supported by the pedestal 162, theactuation assembly 163 provides vertical movement of the lower electrode161 relative to the chamber body 142, the central support member 157,and the upper electrode 112. Such vertical movement of the lowerelectrode 161 within the processing region 102 provides a variable gapbetween the lower electrode 161 and the upper electrode 112, whichallows increased control of the electric field formed therebetween, inturn, providing greater control of the density in the plasma formed inthe processing region 102. In addition, since the substrate 105 issupported by the lower electrode 161, the gap between the substrate 105and the showerhead plate 116 may also be varied, resulting in greatercontrol of the process gas distribution across the substrate 105.

A plasma screen 159 is also provided, supported by the lower electrode161 and overlapping the inner wall 149 of the upper liner assembly 144,to protect the substrate support assembly 160 and the bellows 158 fromthe plasma in the processing region 102. Since the plasma screen 159 iscoupled to and moves vertically with the pedestal 162, the overlapbetween plasma screen 159 the inner wall 149 of the upper liner assembly144 is sufficient to allow the pedestal 162 to enjoy a full range ofmotion without the plasma screen 159 and the upper liner assembly 144becoming disengaged and allowing exposure of the region below thepedestal 162 to become exposed to process gases.

The substrate support assembly 160 further includes a lift pin assembly167 to facilitate loading and unloading of the substrate 105. The liftpin assembly 167 includes lift pins 168 attached to a lift pin plate169. The lift pin plate 169 is disposed within an opening 170 within thelower electrode 161, and the lift pins 168 extend through lift pin holes171 disposed between the opening 170 and the processing region 102. Thelift pin plate 169 is coupled to a lead screw 172 extending through anaperture 173 in the lower electrode 161 and into the hollow pedestal162. An actuator 195 (e.g., motor) may be positioned on the pedestal162. Note, the actuator 195 is shown without hatching to minimizedrawing clutter. The actuator 195 rotates a nut, which advances orretracts the lead screw 172. The lead screw 172 is coupled to the liftpin plate 169. Thus, as the actuator 195 causes the lead screw 172 toraise or lower the lift pin plate 169, the lift pins 168 to extend orretract. Therefore, the actuator 195 allows the lift pins 168 to beextended or retracted regardless of the vertical positioning of thelower electrode 161. By providing such separate actuation of the liftpins 168, the vertical positioning of the substrate 105 can be alteredseparately from the vertical positioning of the lower electrode 161allowing greater control of positioning during both loading andunloading of the substrate 105 as well as during processing of thesubstrate 105, for example, by lifting the substrate during processingto allow backside gas to escape from under the substrate.

The substrate support assembly 160 further includes a vent line 174coupling the opening 170 with the exhaust region 104. The vent line 174is routed centrally through the hollow pedestal 162 and out of thechamber body 142 through one of a plurality of access tubes 180 arrangedin a spoke pattern symmetrical about the central axis (CA) assubsequently described. The vent line 174 provides for evacuation of theopening 170 in order to remove any processing gases that may leak intothe opening 170 via the lift pin holes 171. In addition, evacuation ofthe opening 170 also aids in removing any processing gases that may bepresent on the backside of the substrate 105 disposed on the lowerelectrode 161 or lift pins 168.

The substrate support assembly 160 may also include a gas port 176disposed therethrough and coupled to an inert gas supply 177 via a gassupply line 178. The gas supply 177 supplies an inert gas, such ashelium, through the gas supply line 178 and the gas port 176 to thebackside of the substrate 105 in order to help prevent processing gasesfrom processing the backside of the substrate 105. The gas supply line178 is also routed through the hollow pedestal 162 and out of thechamber body 142 through one of the plurality of access tubes 180.

The substrate support assembly 160 may further include one or more fluidinlet lines 179 and fluid outlet lines 181 routed from a heat exchangefluid source 198 to through one or more heat exchange channels (notshown) in the lower electrode 161 in order to provide temperaturecontrol to the lower electrode 161 during processing. The fluid inletlines 179 and fluid outlet lines 181 are routed from the lower electrode161 through the hollow pedestal 162 and out of the chamber body 142through one of the plurality of access tubes 180.

In one embodiment, the substrate support assembly 160 may furtherinclude one or more temperature sensors 182 disposed in the lowerelectrode 161 to facilitate temperature control of the lower electrode161.

In one embodiment, the lower electrode 161 is an electrostatic chuck,and thus includes one or more electrodes (not shown) disposed therein. Avoltage source (not shown) biases the one or more electrodes withrespect to the substrate 105 to create an attraction force to hold thesubstrate 105 in position during processing. Cabling coupling the one ormore electrodes to the voltage source is routed through the hollowpedestal 162 and out of the chamber body 142 through one of theplurality of access tubes 180.

FIG. 5 is a schematic depiction of the layout of the access tubes 180within spokes 191 of the chamber body assembly 140. Referring to FIGS. 1and 5, the spokes 191 and access tubes 180 are symmetrically arrangedabout the central axis (CA) of the processing apparatus 100 in a spokepattern as shown. In the embodiment shown, three identical access tubes180 are disposed through the chamber body 142 into the central region156 to facilitate supply of a plurality of tubing and cabling fromoutside of the chamber body 142 to the lower electrode 161. In order tofacilitate vertical movement of the lower electrode 162, the opening 183through each of the access tubes 180 is approximately equal to thevertical travel of the lower electrode 161. For example, in oneconfiguration, the lower electrode 162 is vertically movable a distanceof approximately 7.2 inches. In this case, the height of the opening 183in each of the access tubes 180 is also approximately 7.2 inches.Keeping these distances approximately the same helps minimize the lengthof the cabling required as well as preventing binding and wear of thecabling during vertical movement of the lower electrode 161. Inaddition, the width (W) of the spokes 191 is minimized such that a highaspect ratio (height:width) is provided, such that the open area forevacuation passages 189 is enhanced, while still allowing sufficientroom for utilities (e.g., gas, wiring). Such a configuration reducesflow resistance of exhaust gases, resulting in reduced energyconsumption due to pumping and smaller less costly pumps.

In order to further facilitate cable routing to the lower electrode 161,the cable routing is divided between the plurality of access tubes 180.For example, the fluid lines (179, 181), the gas supply line 178, andthe vacuum tube 174 may all be provided through the access tube 180 a;cables for the temperature sensors 182 and other electrical cables(e.g., to actuators 164, 195) may be provided through the access tube180 b; and the RF voltage feed and other electrical cable(s) (e.g., toelectrodes for chucking function) may be provided through the accesstube 180 c. Thus, number and volume of cabling from outside of thechamber body 142 to the lower electrode 162 are divided between theaccess tubes 180 in order to minimize the size of the access tubes 180while providing adequate clearance to facilitate the movement of thelower electrode 161.

The access tubes 180 may be constructed of materials such as aluminum orstainless steel. The symmetrical spoke arrangement of the access tubes180 is designed to further facilitate electrical and thermal symmetry ofthe processing apparatus 100. In one embodiment, the access tubes 180are positioned 120 degrees apart, and each of the access tubes 180 isaligned with a respective gas tube 129. The symmetrical arrangement ofthe access tubes 180 further provides electrical and thermal symmetry inthe chamber body 142, and particularly in the processing region 102, inorder to allow greater more uniform plasma formation in the processingregion 102 and improved control of the plasma density over the surfaceof the substrate 105 during processing.

Referring back to FIGS. 1 and 4, the evacuation passages 189 arepositioned in the upper liner assembly 144 symmetrically about thecentral axis (CA). The evacuation passages 189 allow evacuation of gasesfrom the processing region 102 through the evacuation region 104 and outof the chamber body 142 through an exhaust port 196. The exhaust port196 is centered about the central axis (CA) of the chamber body assembly140 such that the gases are evenly drawn through the evacuation passages189. Evacuation liners 187 may be respectively positioned below each ofthe evacuation passages 189 in evacuation channels 188 provided in thechamber body 142 in order to protect the chamber body 142 fromprocessing gases during evacuation. The evacuation liners 187 may beconstructed of materials similar to that of the upper liner assembly 144as described above.

The evacuation channels 188 are positioned away from the processingregion 102 such that substantially no electrical interaction exists. Thesymmetrical positioning of the evacuation channels 188 about the centralaxis (CA), however, provides improved thermal and gas flow symmetrywithin the processing apparatus 100. For instance, the symmetricalpositioning of the evacuation channels 188 about the central axis (CA),and thus the processing region 102, promotes symmetrical removal ofgases from the processing region 102, resulting in symmetrical flow ofgases across the substrate 105. In addition, the symmetrical positioningof the evacuation channels 188, and the evacuation liners 187, promotessymmetry in the thermal distribution in the chamber. Thus, thesymmetrical positioning of the evacuation channels 188 in the processingapparatus 100 facilitates uniform plasma formation in the processingregion 102 and allows greater control of the plasma density and gas flowin the processing region 102.

The exhaust assembly 190 is positioned adjacent the evacuation region104 at the bottom of the chamber body 142. The exhaust assembly mayinclude a throttle valve 192 coupled to a vacuum pump 194. The throttlevalve 192 may be a poppet style valve used in conjunction with thevacuum pump 194 to control the vacuum conditions within the processingregion 102 by symmetrically drawing exhaust gases from the processingregion 102 through the evacuation passages 189 and out of the chamberthrough the centrally located exhaust port 189, further providinggreater control of the plasma conditions in the processing region 102. Apoppet style valve, as shown in FIG. 1, provides a uniform, 360 degreegap 197 through which evacuation gases are drawn through the exhaustport 196. In contrast, conventional damper-style throttle valves providea non-uniform gap for flow of evacuation gases. For example, when thedamper-style valve opens, one side of the valve draws more gas than theother side of the valve. Thus, the poppet style throttle valve has lesseffect on skewing gas conductance than the traditional damper-stylethrottle valve conventionally used in plasma processing chambers.

Again, referring to FIGS. 1 and 4, a conductive, slant mesh liner 400 ispositioned in a lower portion of the upper liner assembly 144. The slantmesh liner 400 may be constructed from a conductive, process compatiblematerial, such as aluminum, stainless steel, and/or yttria (e.g., yttriacoated aluminum). The slant mesh liner 400 may have a bottom wall 402and an outer wall 404 extending at an outward and upward angle from thebottom wall 402. The outer wall 404 may have a plurality of apertures410 formed therethrough. The apertures 410 may be positionedsymmetrically about a center axis of the slant mesh liner 400 to allowexhaust gases to be drawn uniformly therethrough, which in turn,facilitates uniform plasma formation in the processing region 102 andallows greater control of the plasma density and gas flow in theprocessing region 102. In one embodiment, the central axis of the slantmesh liner 400 is aligned with the central axis (CA) of the chamber bodyassembly 140.

The bottom wall 402 of the mesh liner 400 may be electrically coupled tothe bottom wall 148 and/or the inner wall 149 of the upper linerassembly 144. Additionally, the outer wall 404 of the mesh liner 400 maybe electrically coupled to the outer wall 147 of the upper linerassembly 144. When an RF plasma is present within the processing region102, the RF current seeking a return path to ground may travel along thesurface of the mesh liner 400 to the outer wall 147 of the upper linerassembly 144. Thus, the annularly symmetric configuration of the meshliner 400 provides a symmetric RF return to ground and bypasses anygeometric asymmetries in the lower portion of the upper liner assembly400.

Therefore, embodiments of the present invention solve the problem ofconventional plasma systems with the difficulty in providing uniformplasma density due to asymmetry in the chamber by providing a chamberdesign that allows extremely symmetrical electrical, thermal, and gasflow conductance through the chamber. By providing such symmetry, plasmaformed within the chamber naturally has improved uniformity across thesurface of a substrate disposed in a processing region of the chamber.This improved symmetry, as well as other chamber additions, such asproviding the ability to manipulate the gap between upper and lowerelectrodes as well as between a gas inlet and a substrate beingprocessed, allows better control of plasma processing and uniformity ascompared to conventional systems.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

The invention claimed is:
 1. A plasma processing apparatus, comprising: a lid assembly and a chamber body enclosing a processing region; a substrate support assembly disposed in the chamber body, wherein the lid assembly comprises: an upper electrode having a central manifold configured to distribute processing gas received from a first gas inlet tube into the processing region and one or more annular outer manifolds configured to separately distribute processing gas into the processing region; and an annular ring manifold that is symmetric about a central axis and configured to distribute processing gas received from a second gas inlet tube, and coupled to the one or more annular outer manifolds via a plurality of separate electrically conductive gas tubes that extend between the ring manifold and the upper electrode and are arranged radially and symmetrically outward from the annular ring manifold, the annular ring manifold disposed concentrically around the first gas inlet tube, with the first gas inlet tube passing through the center of the annular ring manifold, and the first gas inlet tube is configured to conduct RF power to the upper electrode, wherein the annular ring manifold is disposed above and spaced apart from the upper electrode.
 2. The plasma processing apparatus of claim 1, wherein the annular ring manifold is comprised of a conductive material.
 3. The plasma processing apparatus of claim 1, wherein the first gas inlet tube is coaxial with a central axis of the substrate support assembly.
 4. The plasma processing apparatus of claim 3, wherein the annular ring manifold circumscribes the first gas inlet tube.
 5. The plasma processing apparatus of claim 4, wherein the annular ring manifold has a recursive gas path so that gas flows equally from the annular ring manifold into the plurality of separate electrically conductive gas tubes.
 6. The plasma processing apparatus of claim 1, wherein the one or more annular outer manifolds circumscribe the central manifold.
 7. The plasma processing apparatus of claim 1, further comprising: a first actuation device coupled to the substrate support assembly and configured to vertically move the substrate support assembly; and a second actuation device coupled to the substrate support assembly and configured to move a plurality of substrate support pins disposed within the substrate support assembly.
 8. A lid assembly for a plasma processing apparatus, comprising: an upper electrode having a central manifold configured to distribute processing gas received from a first gas inlet tube therethrough and one or more outer manifolds configured to separately distribute processing gas therethrough; and an annular ring manifold that is symmetric about a central axis and configured to distribute processing gas received from a second gas inlet, and coupled to the one or more outer manifolds via a plurality of separate electrically conductive gas tubes that extend between the ring manifold and the upper electrode and are arranged radially and symmetrically outward from the annular ring manifold, the annular ring manifold disposed concentrically around the first gas inlet tube, with the first gas inlet tube passing through the center of the annular ring manifold, and the first gas inlet tube configured to conduct RF power to the upper electrode, wherein the annular ring manifold is disposed above and spaced apart from the upper electrode.
 9. The lid assembly of claim 8, wherein the annular ring manifold is comprised of a conductive material.
 10. The lid assembly of claim 8, wherein the first gas inlet tube is coaxial with a central axis of the upper electrode.
 11. The lid assembly of claim 10, wherein the annular ring manifold circumscribes the gas inlet tube.
 12. The lid assembly of claim 11, wherein the annular ring manifold has a recursive gas path so that gas flows equally from the annular ring manifold into the plurality of separate electrically conductive gas tubes.
 13. The lid assembly of claim 8, wherein the one or more outer manifolds circumscribe the central manifold.
 14. A plasma processing apparatus, comprising: a lid assembly and a chamber body enclosing a processing region; a substrate support assembly disposed in the chamber body, wherein the lid assembly comprises: an upper electrode having a central manifold configured to distribute processing gas received from a first gas inlet tube into the processing region and one or more outer manifolds configured to separately distribute processing gas into the processing region; and an annular ring manifold that is symmetric about a central axis and configured to distribute processing gas received from a second gas inlet tube, and coupled to the one or more outer manifolds via a plurality of separate electrically conductive gas tubes that extend between the ring manifold and the upper electrode and are arranged radially and symmetrically outward from the annular ring manifold, the annular ring manifold disposed concentrically around the first gas inlet tube, with the first gas inlet tube passing through the center of the annular ring manifold, and the first gas inlet tube is configured to conduct RF power to the upper electrode; and an exhaust assembly defining an evacuation region within the chamber body, wherein the chamber body includes a plurality of passages symmetrically disposed about the central axis fluidly connecting the processing region with the evacuation region, wherein the annular ring manifold is disposed above and spaced apart from the upper electrode.
 15. The plasma processing apparatus of claim 14, wherein the chamber body has an exhaust port formed therethrough that is symmetric about the central axis of the substrate support assembly. 